 export default function uuidv4() {
     return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
         var r = Math.random() * 16 | 0,
             v = c == 'x' ? r : (r & 0x3 | 0x8);
         return v.toString(16);
     });
 }